Mileah Kromer is a poly sci professor at Elon and assistant director of the Elon University poll. I asked her about voter turnout and Amendment 1, e.g., what would the impact be if Santorum bows out after PA, what's the overall relationship between turnout and the fate of Amendment 1, and so on?
My general thought is this: Citizens use what political scientists call the "calculus of voting" when deciding if and when they will vote. Part of this decision is determined by the probability that their vote will "matter"...so in that case, Santorum/Paul/Gingrich all bowing out could potentially suppress Republican turnout.
That being said, Santorum has done really well with church-going, evangelical Christian voters, who are the core demographic that support same-sex marriage bans. With Santorum out, this could keep some voters home, but at the same time, these voters may be coming to the polls to vote for Amendment 1 independent of any presidential or gubernatorial race.
Amendment 1 will be decided by which side gets their voters to the booth in May. This is a true "get out the vote" situation for both proponents and opponents the amendment. It is time for both sides to start the political "full court press"--phone banking, door-to-door, yard signs, and ramping up all tv/radio/print advertising.